Update system and update method for updating search data

ABSTRACT

A search data update system includes a navigation apparatus in which search data are used and a data provider center that provides the navigation apparatus with update data to be used to update the search data. The update data provided by the data provider center only include new search tree data and update entity data. The new search tree data assume a structure that enables specification of the update entity data and specification of the entity data in the original search data except for the entity data corresponding to the update entity data.

The disclosure of the following priority application is hereinincorporated by reference:

-   Japanese Patent Application No. 2004-051212, filed Feb. 26, 2004

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an update system and an update methodadopted to update search data that are used in a navigation apparatus orthe like.

2. Description of the Related Art

There is a technology known in the related art adopted in a carnavigation apparatus, whereby a map is divided into a plurality ofunits, map data files are created in correspondence to each of the unitsand the map data files are updated in units of the individual files(see, for instance, Japanese Laid Open Patent Publication No.2001-56823). In addition, there is a technology known in the related artadopted to provide map information services through computercommunication, whereby only the map data that need to be newly deliveredare transmitted without transmitting any map data that are alreadypresent in the display memory at a map data display terminal (see, forinstance, Japanese Laid Open Patent Publication No. H 11-295084).

SUMMARY OF THE INVENTION

However, these technologies, which relate to map data update, were notdeveloped by taking into consideration the need for updating search dataused in navigation apparatuses. Search data provided throughcommunication or the like, as well as map data provided throughcommunication or the like, must be updated with a high degree ofefficiency.

The present invention provides an update system and an update methodthat achieve a highly efficient update of search data used in anavigation apparatus or the like.

According to the 1st aspect of the invention, an update system forupdating search data used in a navigation apparatus comprises: anavigation apparatus; and an update data provider apparatus. Thenavigation apparatus comprises a search data acquisition unit thatobtains search data containing first search tree data and a first entitydata group constituted with a plurality of sets of entity data that canbe specified by using the first search tree data, and a control unitthat executes navigation-related processing by using the search data;the update data provider apparatus comprises an update data generationunit that generates at least one set of update entity data and secondsearch tree data assuming a structure that enables specification of theupdate entity data and enables specification of entity data in the firstentity data group other than entity data corresponding to the updateentity data, to be used to update the search data, and a provider unitthat provides the second search tree data and the update entity datahaving been generated to the navigation apparatus; the navigationapparatus further comprises an update data acquisition unit that obtainsthe second search tree data and the update entity data provided by theprovider unit of the update data provider apparatus; and the controlunit in the navigation apparatus executes navigation-related processingby using the second search tree data and the update entity data obtainedby the update data acquisition unit and the entity data in the firstentity data group obtained by the search data acquisition unit.

According to the 2nd aspect of the invention, in the update system forupdating search data used in a navigation apparatus according to the 1staspect, it is preferred that: the provider unit of the update dataprovider apparatus provides the second search tree data and the updateentity data by storing the second search tree data and the update entitydata in a recording medium; and the update data acquisition unit of thenavigation apparatus obtains the second search tree data and the updateentity data stored in the recording medium.

According to the 3rd aspect of the invention, in the update system forupdating search data used in a navigation apparatus according to the 1staspect, it is preferred that: the provider unit of the update dataprovider apparatus provides the second search tree data and the updateentity data via a communication medium; and the update data acquisitionunit of the navigation apparatus obtains the second search tree data andthe update entity data via the communication medium.

According to the 4th aspect of the invention, in the update system forupdating search data used in a navigation apparatus according to eitherone of the 1st through 4th aspects, it is preferred that: the searchdata are named search data, telephone number search data or mailingaddress search data.

According to the 5th aspect of the invention, in the update system forupdating search data used in a navigation apparatus according to eitherone of the 1st through 5th aspects, it is preferred that: the searchdata are managed in units of files each corresponding to a specificunit; and the second search tree data and the update entity data used toupdate search data in each file are provided in a single file.

According to the 6th aspect of the invention, a navigation apparatus isa navigation apparatus that constitutes an update system for updatingsearch data used in a navigation apparatus according to either one ofthe 1st trough 5th aspects.

According to the 7th aspect of the invention, an update data providerapparatus is an update data provide apparatus that constitutes an updatesystem for updating search data used in a navigation apparatus accordingto either one of the 1st through 5th aspects.

According to the 8th aspect of the invention, an update method forupdating search data stored in a single file containing search tree dataand a plurality of sets of entity data that can be specified by usingthe search tree data, comprises: generating at least one set of updateentity data to be used to update the search data; generating new searchtree data assuming a structure that enables specification of the updateentity data and specification of the plurality of sets of entity data inthe file other than entity data corresponding to the update entity data;and providing the update entity data and the new search tree data inanother file different from the single file.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an update system adopted to update search data used in anavigation apparatus;

FIG. 2 is a block diagram of an on-vehicle navigation apparatus;

FIGS. 3A and 3B illustrate a method adopted to update a single searchdata file;

FIG. 4 illustrates how information related to a search data update isexchanged between the navigation apparatus and the data provider center;

FIG. 5 presents a flowchart of the search processing executed in thenavigation apparatus;

FIG. 6 illustrates the comparison processing executed by using thesearch tree for the name search data; and

FIG. 7 illustrates how the control program may be provided.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows the update system achieved in the embodiment to updatesearch data used in a navigation apparatus. An on-vehicle navigationapparatus 1 reads map data, search data (guide search data) and the likefrom a recording medium 2, which may be a CD-ROM or a DVD-ROM. A server6 at a data provider center 9 reads map data and search data from a mapdatabase 7 and a search database 8 respectively and provides update datafor the map data and the search data to the navigation apparatus.

The navigation apparatus 1 can connect with a communication device 4such as a portable telephone. The navigation apparatus 1 can alsoconnect with a telephone network 5 via the communication device 4 andcan further connect with the server 6 via the telephone network 5. Atthe server 6, map data from old versions to the latest version are savedin the map database 7 and search data from old versions to the latestversion are saved in the search database 8. Thus, the server 6 is ableto provide update data to be used to update part of the map data or thesearch data at the navigation apparatus 1 via the telephone network 5.

The navigation apparatus 1 includes a control device 11 and anonvolatile memory 12. The control device 11 is constituted with amicroprocessor and its peripheral circuits. The nonvolatile memory 12may be a hard disk provided as an internal component of the navigationapparatus 1 or it may be a nonvolatile memory such as a flash memory.The nonvolatile memory 12 may assume any form as long as it constitutesa storage device that holds the data written therein intact even whenthe power to the navigation apparatus 1 is turned off.

The map database 7 and the search database 8 at the data provider center9, which hold all the versions including the original versions and themost recent versions of map data and search data, may be regarded asdatabases of mother data. The server 6 is also able to prepare arecording medium 2 holding therein initial (non-updated) map data orsearch data by using the data at the map database 7 or the searchdatabase 8.

FIG. 2 is a block diagram of the on-vehicle navigation apparatus 1. Thenavigation apparatus 1 comprises the control device 11, the nonvolatilememory 12, a current position detection device 13, a DVD drive device14, a memory 15, a communication interface 16, an input device 17, amonitor 18 and the like.

The current position detection device 13, which detects the currentposition of the vehicle, may be constituted with, for instance, anazimuth sensor that detects the advancing azimuth of the vehicle, avehicle speed sensor that detects the vehicle speed, a GPS sensor thatdetects a GPS signal transmitted from a GPS (global positioning system)satellite and the like. The DVD drive device 14 reads map data and thelike in the recording medium 2 loaded therein. In the embodiment, therecording medium 2 is a DVD-ROM. However, the recording medium 2 may bea CD-ROM or another type of recording medium.

The memory 15 is used to store the vehicle position information detectedwith the current position detection device 13 and the like and also tostore node information, link information and the like of the nodes andthe links on a recommended route calculated by the control device 11.The memory 15 constitutes a working area for the control device. Thecommunication interface 16 is used to achieve a connection with thecommunication device 4. The use of a portable telephone and an Internetconnection are enabled via the communication interface 16.

At the monitor 18 a map, a recommended route and various types ofinformation are displayed. The monitor 18 may be provided as anintegrated part of the navigation system main unit or it may be providedas a separate encased unit. In addition, the monitor 18 disposed at anisolated position may be connected to the navigation system main unitthrough a cable or the like. Through the input device 17, thedestination for the vehicle and the like are entered when conducting aroute search. It is also used when entering search keys. It may beconstituted as a remote-control unit or it may be constituted as a touchpanel disposed on the screen at the monitor 18.

The control device 11 executes various types of navigation processingsuch as road map display, route calculation (route search) and routeguidance by using the current vehicle position information detected withthe current position detection device 13, the map data and the searchdata stored in the recording medium 2 or the nonvolatile memory 12. Itis to be noted that a program of the various types of processingexecuted by the control device 11 is installed in a ROM (not shown)provided inside the control device 11.

The server 6 at the data provider center 9 is a computer system thatexecutes various types of processing including delivery of update databy using the map database 7 and the search database 8. The computersystem constituting the server 6 may be any of various types ofcomputers including general-purpose computers, workstations and personalcomputers.

Next, an explanation is given on the map data and the search data usedin the navigation apparatus 1.

—Map Data—

The map data are information related to maps and include background (formap display) data, road (locator) data, route search data (network data)and route guidance data (information indicating intersection pointnames, road names, directional terms, directional guidance facilityinformation and the like). The background data are used to display abackground of a road or a background in a road map. The road data areused to specify the current vehicle position on the road, for mapmatching and the like. The route search data, which are constituted withbranching information and the like not directly relevant to the specificroad shapes, are mainly used when calculating a recommended route (whenexecuting a route search). The route guidance data include the names ofintersection point and the like, and are used to provide guidance forthe driver or the like along the calculated recommended route.

The road data (locator data) are link string data with which roads areeach expressed as a link string containing links and nodes. A node maybe an intersection point or a specific point that is specially set onthe road. A link corresponds to the portion of the road between twonodes and a given road is expressed as a string of a plurality of links(a link string). Details of link string data are known in the relatedart. The background data are, for instance, polygon data and polylinedata. A road is displayed by using polyline data.

—Search Data—

The search data are not used to specify a desired point on the map, butare used to determine a desired point through a search. For instance,when executing a route search, the user can enter the name, thetelephone number, the address or the like of a specific facility and theposition of the facility determined by using the search data can be setas the destination. The control device 11 sets the geographic pointdetermined by using the search data as the destination and executesprocessing such as a route search.

The search data includes various types of data, such as name (phonetic)search data, telephone number search data and address search data. Thename search data, which are used to specify the positions of facilitieson the map by name, are provided as data files each created incorrespondence to a given category for each prefecture. There arevarious categories such as “rail station”, “airport”, ferry″,“department store”, “hotel” and “gas station”. Each file contains searchtree data that allow a name-based search and entity data.

The telephone number search data, which are used to specify thepositions of facilities on a map by their telephone numbers, areprovided as data files each corresponding to a specific combination ofthe first two digits of the area code. Each file contains search treedata that allow a telephone number-based search and entity data. Themailing address search data, which are used to specify the positions offacilities on the map by their mailing addresses, are provided as datafiles, each corresponding to a specific municipality in a givenprefecture. Each file contains search tree data that allow a mailingaddress-based search and entity data. The entity data in the varioustypes of search data contain name information, telephone numberinformation, mailing address information, positional information and thelike corresponding to the individual facilities. It is to be noted thatthe positional information in the search data is positional coordinatedata that indicate the positional coordinates of the facilities by theirlatitudes and longitudes or the like. The entity data may be referred toas facility data, site data or search-object data.

—Update of Search Data—

FIG. 3 illustrates the method adopted in the embodiment to update agiven search data file. FIG. 3A shows a pre-update name search data file21, which may be the name search data file for the category “gasstation” in “Kanagawa Prefecture”. The name search data file 21 is asingle data file with which data read/write and the like are managed.

The name search data file 21 is constituted with search tree data A 22and a entity data group 23 that includes a plurality of sets of entitydata. The search tree data A22 are data adopting a hierarchicallylayered structure (tree structure), which are provided to enable asearch for desired entity data by the name. The search tree data A 22are used to specify (search for) a set of or a plurality of sets ofentity data corresponding to the specified name(s). The entity datagroup 23 includes a plurality of sets of entity data. In the examplepresented in FIG. 3A, the entity data group 23 includes a plurality ofsets of entity data such as entity data 24 for a gas station ABC, entitydata 25 for a gas station BBB, entity data 26 for a gas station CCC,entity data 27 for a gas station DDD and entity data 28 for a gasstation EEE. Each set of entity data contain information indicating thename, the telephone number, the mailing address, the position and thelike of the corresponding facility (business establishment or the like).

The following explanation focuses on an update of the name search datafile 21 for the category “gas station” in Kanagawa Prefecture. Let usnow assume that the name search data file is to be updated by deletingthe entity data 26 for the gas station CCC and adding new entity datafor gas stations ACC and GG.

FIG. 3B shows an update data file 31 created to execute this update. Theupdate data file 31 includes search tree data B 32 and update entitydata 33. The update entity data 33 only include entity data 34 for thegas station ACC and entity data 35 for gas station GG, which are to beadded. The search tree data B 32 are structured so as to enablespecification of entity data in the entity data group 23 in the namesearch data file 21 and entity data in the update entity data 33. Thename search data file 21 in FIG. 3A is left intact.

Namely, the name search data file 21 is not updated by generating a newname search data file having a new entity data group that no longerincludes the entity data 26 for the gas station CCC but includes theadditional entity data 34 and entity data 35 for the gas stations ACCand GG and new search tree data with which entity data in the new entitydata group can be specified. Instead, the name search data file 21 isleft intact and the update data file 31 that only contains another setof search tree data B 32 and the additional entity data 34 and 35 to beused for the update is simply added in the embodiment. It is to be notedthat since the new search tree data B 32 assume a structure which doesnot allow specification of the entity data 26 for the gas station CCC,no problem arises even if the entity data 26 for the gas station CCCremain in the name search data file 21.

As a result, the volume of data that must be provided for the searchdata update is reduced. This, in turn, makes it possible to reduce thecommunication cost necessitated by the data update, the length ofcommunication time and the length of time required to execute the updateprocessing.

For instance, let us assume that the name search data file 21 containsthe search tree data 22 amounting to 10 MB (megabytes) and the entitydata group 23 amounting to 10 MB, and thus, the size of the entire namesearch data file 21 is 20 MB. It is also assumed that the volume of eachset of entity data is approximately 1 KB (kilobyte) and that the volumeof the search tree data used to specify entity data increases to 11 MBafter the update.

If the entire name search data file 21 was regenerated, the size of thenew name search data file 21 would be 21.1 MB, the makeup of which wouldinclude 11 MB (the new search tree data), 10 MB (the pre-update entitydata group 23) and 2 KB (the additional entity data for the gas stationsACC and GG)—1 KB (the deleted entity data for the gas station CCC). Thesize of the update data file 31 generated by adopting the update methodin the embodiment, on the other hand, is only 11.2 MB, the makeup ofwhich includes 11 MB (the new search tree data) and 2 KB (the additionalentity data for the gas stations ACC and GG). Namely, while it would benecessary to provide 21.1 MB of data to update the name search data file21 if the entire name search data file 21 was to be re-created fromscratch, only 11.2 MB of data need to be provided in the update methodachieved in the embodiment.

FIG. 4 shows how information needed to update search data is exchangedbetween the navigation apparatus 1 and the data provider center 9. Theprocessing at the navigation apparatus 1 is executed by the controldevice 11 in conformance to a specific program. The processing at thedata provider center 9 is executed by the server 6 in conformance to aspecific program. The processing at the navigation apparatus 1 in FIG. 4starts as a menu item “search data update” is selected in a menu screenor the like at the navigation apparatus 1.

In step S1, the control device 11 in the navigation apparatus 1 selectsthe type of search data to undergo the update. For the search data typeselection, a data classification (type) selection screen is brought upon display at the monitor 18. Then, the operation waits for the user toselect the type of data to be updated through the input device 17. Thedata classification selection screen may include options such as “namesearch data”, “telephone number search data” and “mailing address searchdata” so as to allow the user to select one of the options. Then, inresponse to the selection made by the user, the data type is specified(selected).

In step S2, the control device 11 in the navigation apparatus 1 promptsthe user to verify the update area. More specifically, it may provide amessage “specify area for search data update” as an audio output or as avisual prompt displayed on the monitor 18. At the monitor 18, a mapscreen with a cursor is brought up on display. The user uses the inputdevice 17 to scroll the map screen up/down and left/right so as to setthe cursor on the desired area (geographic point). Once the cursor isset at the desired area (geographic point), a confirm button is operatedto specify the update area (geographic point, position).

In step S3, the control device 11 in the navigation apparatus 1identifies the correct search data file corresponding to the specifiedupdate area (geographic point). If there is an update data file, theupdate data file, too, is identified. The update data file is assignedwith a file name that achieves a specific correlation with the file nameof the search data file.

From the search data file and the update data file thus identified,version information (editions, update dates, data generation dates andthe like) is obtained. If there is an update data file, the version ofthe update data file is regarded as the most recent version of thesearch data file. If there is a plurality of update data files, theversion of the most recent update data file is regarded as the latestversion of the search data file.

In step S4, the control device 11 in the navigation apparatus 1 issuesan update request to the data provider center 9. More specifically, itimplements control on the portable telephone constituting thecommunication device 4 via the communication interface 16 so as tooriginate a phone call to the data provider center 9 from the portabletelephone. Once the call is connected, the update request istransmitted. The update request is issued by transmitting informationindicating the type of search data to be updated, the file name of thesearch data file and the version of the search data file and also theversion information indicating the update data file version if there isany update data file. The communication between the navigation apparatus1 and the data provider center 9 is achieved by using a digital datacommunication function of the portable telephone.

In step S11, the server 6 at the data provider center 9 verifies therequest transmitted from the navigation apparatus 1. Namely, it obtainsthe information indicating the search data type, the file name of thesearch data file and the like and the version information having beentransmitted, and then the operation proceeds to step S12.

In step S12, the server 6 at the data provider center 9 accesses thesearch database 8 and makes a decision as to whether or not there is anew version of the search data corresponding to the search data filebased upon the information indicating the search data type and thesearch data file name and the like and the version information havingbeen obtained. The presence of a new version of the search dataindicates that entity data have been added, modified or deleted and thatthere are search tree data newly generated to enable specification ofentity data following such addition, modification or deletion.

If it is decided in step S12 that there is a new version of the searchdata, the operation proceeds to step S13, whereas the operation proceedsto step S14 if it is decided that there is no new version of the searchdata. In step S13, the server 6 at the data provider center 9 generatesupdate data. The update data are constituted of the update data file 31explained earlier.

In step S14, the server 6 at the data provider 9 transmits the updatedata (the update data file) generated in step S13 to the navigationapparatus 1. It is to be noted that if it is decided in step S12 thatthere is no version of the search data, data indicating the absence of anew version of the search data are transmitted.

In step S5, the control device 11 in the navigation apparatus 1 executesupdate processing on the search data. In more specific terms, it storesthe update data file transmitted thereto into the nonvolatile memory 12.If data indicating that there is no new version of the search data havebeen transmitted, a message indicating the absence of a new search dataversion is displayed at the monitor 18.

—Search Processing—

FIG. 5 presents a flowchart of the search processing executed at thenavigation apparatus 1. The search processing is executed by using thename search data in FIG. 5. As the user enters specific characters oneat a time through the input device 17, the facility name matching theentered characters is searched. It is to be noted that the explanationis given in reference to FIG. 5 by assuming that the category and thearea corresponding to the search subject have already been specified.Namely, it is assumed that a specific search data file has already beenidentified.

In step S21, the control device 11 makes a decision as to whether or notthere is any update data file related to the subject search data file.Namely, it makes a decision as to whether or not update processing hasbeen executed previously for the subject search data file. If an updatedata file related to the subject search data file is stored, it isjudged that update processing has been executed previously.

If it is decided in step S21 that there is no update data file, theoperation proceeds to step S22, whereas the operation proceeds to stepS23 if it is decided that there is an update data file. In step S22, thesearch tree data in the name search data file, i.e., the original searchtree data are obtained and then the operation proceeds to step S24. Instep S23, the search tree data in the update data file are obtainedbefore the operation proceeds to step S24. If there is a plurality ofupdate data files, the search tree data in the update data file in themost recent version are obtained.

The search tree data in the name search data file are read from the namesearch data file stored in the recording medium 2. The search tree datain the update data file are read from the nonvolatile memory 12. Thesearch tree data having been read are stored into the memory 15, andsubsequently, comparison processing and the like are executed by usingthe data in the memory 15. It is to be noted that the data file in therecording medium 2 may be first read out into the nonvolatile memory 12and, in such a case, the data file can be obtained by accessing thenonvolatile memory 12 as is the update data file.

In step S24, the control device 11 obtains the character having beenentered by the user through the input device 17. In step S25, thecomparison processing is executed on the first character having beenentered by using the search data. Namely, the search tree data havingbeen obtained are used to execute the comparison processing for thecharacter.

FIG. 6 illustrates the comparison processing executed by using thesearch tree data in the name search data. The search tree is constitutedwith a single root cell table 41 and a plurality of cell tables 42through 44. While alphabetic characters are used, e.g., the gas stationABC, in the names of the gas stations in the example presented in FIG.3, the Japanese alphabet system hiragana is used in the explanationgiven in reference to FIG. 6. However, the same basic principle applies,whether the names are written by using alphabetic characters or hiraganacharacters. The same principle also applies to names written by usingnumerical characters or katakana characters. And also alphabeticcharacters of any language of any country may be used. In case ofEnglish alphabet, Japanese hiragana characters “a”, “i”, “u”, “e”, “o”and so on can be replaced with English alphabet characters “a”, “b”,“c”, “d”, “e” and so on in the following explanation.

The root cell table 41 is a table of the first characters (leadingcharacters) in the facility names. “Symbol” assigned with referencenumeral 51 in the root cell table indicates first characters of facilitynames, and in the example presented in FIG. 6, three differentcharacters, “a”, “ka” and “sa”, are listed as the first characters. Anumber of searches 52 indicates the number of sets of entity dataavailable in correspondence to each character. As “pointer” 53, apointer to a lower-order cell table or a pointer to entity data isentered. In the example presented in FIG. 6, pointers to lower-ordercell tables indicate characters A, B, C, . . . , assigned to theindividual cell tables, whereas pointers to entity data each indicatethe number assigned to a specific entity table and the number assignedto the specific entity data in the entity table.

It is to be noted that new search tree data are generated while thepre-update entity data group is left intact and new update entity dataare added, as described earlier to update search data in the embodiment.The cell tables 41 through 44 in the search tree in FIG. 6 correspond tothe search tree data B 32 in FIG. 3B, the entity table 1 (45) in FIG. 6corresponds to the entity data group 23 in FIG. 3A, and the entity table2 (46) in FIG. 6 corresponds to the update entity data 33 in FIG. 3B.

The cell table A 42 in FIG. 6 is a table specified by the pointercorresponding to the symbol “a” in the root cell table 41. In thisexample, “a”, “i” and “ma” are listed as characters that come after thefirst character “a”, and the corresponding numbers of sets of entitydata are 7, 10 and 7 respectively. “BLANKS” indicates that there is nofurther character following the first character “a”, and thecorresponding number of searches indicates that there are three sets ofentity data for the name constituted with the character “a” alone. Thepointer for “BLANKS” points to the leading portion of the correspondingset of entity data in the entity table.

The cell table B 43 is a table specified by the pointer corresponding tothe character “a” in the cell table 42. In this example, “su”, “chi” and“wa” are listed as characters that come after the first two characters“a”“a”, and the corresponding numbers of sets of entity data are 1, 3and 1 respectively. “BLANKS” indicates that there is no furthercharacter following the first character “a”“a”, and the search numberindicates that there are two sets of entity data corresponding to thename constituted with the character “a” alone. The pointer for “BLANKS”points to the leading portion of the corresponding set of entity data inthe entity table. The cell table C 44 assumes a similar structure.

In step S25, the relevant cell tables are identified each incorrespondence to one of the characters having been entered and thesearch is thus carried out by using the cell tables in the search treedescribed above. In step S26, the number of sets of search data that canbe searched, as determined through the processing in step S25 isindicated at the monitor 18. Namely, the number of facilities havingnames written with leading characters matching the characters havingbeen input thus far is indicated.

In step S27, a decision is made as to whether or not the character entryhas been completed. More specifically, a decision is made as to whetheror not a search button disposed at the input device 17 or the like hasbeen pressed. If it is decided that the character entry has not beencompleted, the operation returns to step S24 to continuously execute theprocessing. If, on the other hand, it is decided that the characterentry has been completed, the operation proceeds to step S28.

In step S28, the matching entity data are extracted and their contentsare displayed. Namely, a list of the entity data extracted based uponthe results of the comparison of the entered characters with the searchtree executed in step S25 is displayed at the monitor 18. The cell tablepointer needs to contain data that enable a data access bydistinguishing the entity data group in the original search data filefrom the update entity data when extracting the matching entity data.For instance, an identifier to be used to identify the entity data inthe search data file as distinct from the entity data in the update datafile may be attached. This identifier may be constituted of the firstnumeral indicated in the pointer data, such as “1” in 1-n or “2” in 2-1.Alternatively, the identifier may directly indicate the search data filename or the update data file.

The user selects one candidate from the search results brought up ondisplay. In more specific terms, the user moves the cursor on themonitor 18 by using the input device 17, sets the cursor at the desiredsearch candidate and presses the confirm button. As a result, one of thecandidates indicated as the search results is selected. Thus, adestination, for instance, can be set by using the search data.

The following advantages are achieved by adopting the update system forupdating search data explained above.

-   (1) When search data are updated, only new search tree data and    update entity data are generated. In other words, the original    entity data are retained and used as long as no change has been made    in the entity data. As a result, the volume of data that need to be    provided to update search data can be reduced. This, in turn, makes    it possible to reduce the communication cost necessitated by the    update, the length of communication time and the length of time    required to execute the update processing. It is to be noted that    the new search tree data assume a structure that allows    specification of update entity data and specification of the    original entity data unaffected by the update.-   (2) Since data are updated in units of individual files, the update    can be executed with ease and the update management, too, is    facilitated. In addition, since a file that needs to be updated    alone can be specified, it is possible to obtain the absolute    minimum volume of update data to simplify the process of update data    acquisition and save time and money when obtaining the update data.-   (3) Since the original search data files are retained intact in the    navigation apparatus 1, old search data can be referenced easily    whenever necessary.-   (4) The data provider center 9 ascertains the most recent version of    data held in the navigation apparatus 1 and transmits data only if    there is a newer version of data than the version held at the    navigation apparatus 1. As a result, a transmission of redundant    update data is not executed.

While an explanation is given above in reference to the embodiment on anexample in which name search data are updated, the present invention maybe adopted equally effectively when updating other types of search data.

While an explanation is given above in reference to the embodiment on anexample in which the navigation apparatus 1 and the data provider center9 are connected through the telephone network 5, the present inventionis not limited to this example and the navigation apparatus and the dataprovider center may be connected through another communication line(communication medium). For instance, they may be connected with eachother via the Internet or they may be connected by using a dedicatedline.

While an explanation is given above in reference to the embodiment on anexample in which update data (update data files) are provided via thecommunication line (communication medium) in the telephone network 5,the present invention is not limited to this example. Update data(update data files) may instead be provided in a recording medium suchas a CD-ROM or a memory card.

While an explanation is given above in reference to the embodiment on anexample in which search data are managed in units of files and areupdated in units of individual files, the present invention is notlimited to this example. For instance, search data may be updated andmanaged by further dividing each file into even smaller data portionunits. Namely, the search data may be managed and updated in any unitsas long as the search data update can be managed effectively in suchunits.

While an explanation is given above in reference to the embodiment on anexample in which the search data include name search data, telephonenumber search data and mailing address search data, the presentinvention is not limited to this example, and the search data mayinclude another type of search data. Namely, the present invention maybe adopted in conjunction with any type of search data that can be usedto identify specific positions.

In the embodiment explained above, the name search data are provided inthe form of data files each corresponding to a specific category for agiven prefecture, the telephone number search data are provided in theform of data files each corresponding to a specific combination of thefirst two digits of the area code and the mailing address search dataare provided in the form of data files each corresponding to one of themunicipalities in a given prefecture. However, the present invention isnot limited to these examples, and data files may be generated incorrespondence to other units.

While an explanation is given above in reference to the embodiment on anexample in which the DVD drive device 14 is installed at the navigationapparatus 1, the present invention is not limited to this example. Thenavigation apparatus 1 may include the nonvolatile memory 12 such as ahard disk alone, and all the map data and the search data may beacquired through communication. Alternatively, and IC card slot or thelike may be provided at the navigation apparatus 1 so as to allow updatedata used to update search data to be provided in a removable memorysuch as an IC card.

While an explanation is given above in reference to the embodiment on anexample in which the navigation apparatus is the type that is installedin a vehicle, the present invention is not limited to this example. Forinstance, the present invention may be adopted in conjunction with aportable navigation apparatus, instead.

While an explanation is given above in reference to the embodiment on anexample in which the programs executed by the navigation apparatus 1 andthe server 6 are already installed in the respective apparatuses, thepresent invention is not limited to this example. These programs may beprovided in recording media such as DVDs or CD-ROMs. In such a case,each apparatus must include a data read device capable of reading thedata from the recording medium. Alternatively, the programs may beprovided via a transmission medium such as a communication line, atypical example of which is the Internet. In other words, the programsmay be converted to and transmitted as signals on a carrier wave onwhich the transmission medium is carried.

While an explanation is given above in reference to the embodiment on anexample in which the present invention is adopted in conjunction with adedicated navigation apparatus installed in a vehicle, the presentinvention is not limited to this example. The control program for thenavigation apparatus 1 described above may be executed on a personalcomputer to realize the navigation apparatus in the personal computer.In such a case, the current position detection device 13 and the likeshould be connected to a specific I/O port of the personal computer.

When the present invention is adopted in a personal computer or thelike, the control program may be provided in a recording medium such asa CD-ROM or a DVD-ROM or as a data signal on the Internet or the like.FIG. 7 shows how this may be achieved. A personal computer 100 receivesthe program via a CD-ROM 104. In addition, the personal computer 100 hasa function that allows it to be connected with a communication line 101.A computer 102 is a server computer that provides the program stored ina recording medium such as a hard disk 103. The communication line 101may be a communication line for Internet communication, personalcomputer communication or the like, or it may be a dedicatedcommunication line. The computer 102 reads out the program from the harddisk 103 and transmits the program to the personal computer 100 via thecommunication line 101. Namely, the program is embodied as a data signalon a carrier wave and is transmitted via the communication line 101. Inother words, the program can be distributed as a computer-readablecomputer program product adopting any of various modes such as arecording medium and a carrier wave.

They above described embodiment is an example, and various modificationscan be made without departing from the spirit and scope of invention.

What is claimed is:
 1. An update system for updating search data used ina navigation apparatus, comprising: a navigation apparatus; and anupdate data provider apparatus, wherein: the navigation apparatuscomprises a search data acquisition unit that obtains search datacontaining first search tree data and a first entity data groupconstituted with a plurality of sets of entity data that can bespecified by using the first search tree data, and a control unit thatexecutes navigation-related processing by using the search data; theupdate data provider apparatus comprises an update data generation unitthat generates at least one set of update entity data and second searchtree data assuming a structure that enables specification of the updateentity data and enables specification of entity data in the first entitydata group other than entity data corresponding to the update entitydata, to be used to update the search data, and a provider unit thatprovides the second search tree data and the update entity data havingbeen generated to the navigation apparatus; the navigation apparatusfurther comprises an update data acquisition unit that obtains thesecond search tree data and the update entity data provided by theprovider unit of the update data provider apparatus; and the controlunit in the navigation apparatus executes navigation-related processingby using the second search tree data and the update entity data obtainedby the update data acquisition unit and the entity data in the firstentity data group obtained by the search data acquisition unit.
 2. Anupdate system for updating search data used in a navigation apparatusaccording to claim 1, wherein: the provider unit of the update dataprovider apparatus provides the second search tree data and the updateentity data by storing the second search tree data and the update entitydata in a recording medium; and the update data acquisition unit of thenavigation apparatus obtains the second search tree data and the updateentity data stored in the recording medium.
 3. An update system forupdating search data used in a navigation apparatus according to claim1, wherein: the provider unit of the update data provider apparatusprovides the second search tree data and the update entity data via acommunication medium; and the update data acquisition unit of thenavigation apparatus obtains the second search tree data and the updateentity data via the communication medium.
 4. An update system forupdating search data used in a navigation apparatus according to claim1, wherein: the search data are named search data, telephone numbersearch data or mailing address search data.
 5. An update system forupdating search data used in a navigation apparatus according to claim1, wherein: the search data are managed in units of files eachcorresponding to a specific unit; and the second search tree data andthe update entity data used to update search data in each file areprovided in a single file.
 6. A navigation apparatus that constitutes anupdate system for updating search data used in a navigation apparatusaccording to claim
 1. 7. An update data provider apparatus thatconstitutes an update system for updating search data used in anavigation apparatus according to claim 1.